But B cannot rest on the second day, or A would be left without the article which B produces. Nor is there any means of making the exchange just, unless a third labourer is called in. Then one workman, A, produces a, and two, B and C, produce b:—A, working three hours, has three a;—B, three hours, 1-1/2 b;—C, three hours, 1-1/2 b. B and C each give half of b for a, and all have their equal daily maintenance for equal daily work.
To carry the example a single step farther, let three articles, a, b, and c be needed.
Let a need one hour's work, b two, and c four; then the day's work must be seven hours, and one man in a day's work can make 7 a, or 3-1/2 b, or 1-3/4 c.
Therefore one A works for a, producing 7 a; two B's work for b, producing 7 b; four C's work for c, producing 7 c.
A has six a to spare, and gives two a for one b, and four a for one c. Each B has 2-1/2 b to spare, and gives 1/2 b for one a, and two b for one c.
Each C has 3/4 of c to spare, and gives 1/2 c for one b, and 1/4 of c for one a.
And all have their day's maintenance.
Generally, therefore, it follows that if the demand is constant,[31] the relative prices of things are as their costs, or as the quantities of labour involved in production.
64. Then, in order to express their prices in terms of a currency, we have only to put the currency into the form of orders for a certain quantity of any given article (with us it is in the form of orders for gold), and all quantities of other articles are priced by the relation they bear to the article which the currency claims.